PASADENA, Calif. — Scientists are impressed with the flood of data beamed back by NASA's most advanced Mars orbiter.

The space agency said Wednesday that the Mars Reconnaissance Orbiter has sent back 100 terabits of information since 2006. That's equal to 100 trillion bits of data — the equivalent of about 3 million songs in MP3 format, or 35 hours of uncompressed high-definition video.

To put it another way, that's more than three times the total amount of data sent back by all the previous missions that have flown past the orbit of Earth's moon.

Launched from Florida in 2005, the orbiter reached Mars in March 2006. It is the most powerful probe ever sent to the Red Planet.

"What is most impressive about all these data is not the sheer quantity, but the quality of what they tell us about our neighbor planet," the orbiter's project scientist, Rich Zurek of NASA's Jet Propulsion Laboratory, said in a mission update. "The data from the orbiter's six instruments have given us a much deeper understanding of the diversity of environments on Mars today and how they have changed over time."

Among the mission's major achievements is the finding that water has had an effect on or near the surface of Mars for hundreds of millions of years. This activity was at least regional and possibly global in extent, though possibly intermittent.

The spacecraft has also observed signatures of a variety of watery environments, some acidic, some alkaline. Such observations increase the likelihood that future probes could find evidence of past life on Mars, if it ever existed.

Last year, Mars Reconnaissance Orbiter suffered several computer resets that temporarily halted science operations. It has since returned to normal.